Device for mixing and casting

ABSTRACT

A device for mixing and dispensing a mass of castable material includes a mixing container having a dispensing section formed at the bottom thereof. A mixing member is mounted within the container to be actuated vertically relative thereto to effect mixing of the castable mass and vacuum means are provided for drawing off gases accumulated within the container during mixing. A closure member including a piston is mounted upon the mixing member to be movable relative thereto. The closure member sealingly engages dispensing section of the container to prevent outflow of material during mixing and is disengageable therefrom to enable dispensing of the mixed castable mass.

United States Patent [191 Hiiuser [4 1 Nov. 27, 1973 [54] DEVICE FOR MIXING AND CASTING 2,813,300 ll/1957 Hausman 259/98 4 12 l 75 Inventor: Erhard Hauser, Schwalbach, 84204 969 Came 259/27 Germany 7 Primary Examiner--Robert W. Jenkins [73] As'signee: Arthur Vakuumtechnik Pfeiffer Att0rneyDavid Toren GmbH, Wetzlar, Germany [22] Filed: Apr. 17, 1972 I ABSTRACT v [21 1 A I No 244 799 A device for mixing and dispensing a mass of castable pp material includes a mixing container having a dispensing section formed at the bottom thereof. A mixing [30] Foreign Application Priority Data member is mounted within the container to be actu- Apr. 17, 1971 Germany P 21 1 74 1 ated'vertically relative thereto to effect mixing of the castable mass and vacuum means are rovided for [52] us. Cl. 259/4, 259/47 ng ff g e a m l ed within the container [51] Int. Cl Bolt 15/02 r g m g- A l r mem r in l ing a piston is [58] Field of Search 259/1, 2, 4, 36, mounted p n th mixing member to be movable rela- 259/27, 47, 97, 98 tive thereto. The closure member sealingly engages dispensing section of the container to prevent outflow [56] References Cit d of material during mixing and is disengageable there- UNITED STATES PATENTS from to enabledispensing of the mixed castable mass.

831,813 9/1906 Weber 259/2 18 Claims, 4 Drawing Figures 40 [I 39 56 43 3/ 29 28 i. 54 33 50 Z- 33 2? I3 g 5 I 49 v 2! 4B 20 9 l l5 ,4 c I6 17 l8 PATENTEBnnve'v ms SHEET 2 BF 2 The invention relates to a device for mixing of a plurality of components into a flowable mass which is dispensed for casting this mass, with a container for re ceiving the mass, a mixing member, a tapping region arranged at the bottom of the container and a connection for a vacuum pump.

In the working of casting resin masses, the procedure is frequently that the constituents to be reacted together are brought together in a suitable mixer and are mixed with each other. In this respect, it is frequently important that during the mixing procedure the taking up of gases, especially from the air is avoided, or that gases dissolved in the liquid components are removed, in order to give the mixture which becomes solid by chemical reaction after casting, predetermined quality characteristics for example high dielectric values. After the mixing procedure, the still flowable mass usually has to be distributed in small individual portions into moulds.

Mixers are shown with rotatable mixing members. These mixers are of vacuum tight construction and have at their bottom, as a closure, a blocking member in the form of a valve or tap. These mixers are evacuated by a vacuum pump so that the dissolved gases leave the mass during the mixing procedure. For a distribution of the ready mixed and de-gassed mass, the

. fected with thesemixers, unless specially constructed dosing pumps are connected subsequent to the mixer and the blocking member. In such cases, the interruption of the vacuum in the mixer is a rule essential in I order to ensure the flow to the dosing pump. However,

also when casting under atmospheric pressure, the vacuum in the mixer has to be interrupted. Also, the mixing and de-gassing procedure in the known mixers is often unsatisfactory, since the bubbles occurring in the I ing for the preparation of components which are fed together into the ready mixer. In this known arrangement, the preliminary mixers have a mixing member which is movable to and fro between two end positions along a risingly oriented line. At the lower end of the mixing container, there is arranged a piston pump whose cylinder extends into the material contained in the mxing container and the piston of which, when disposed at the suction stroke dead centre, releases a flow connection of large cross section between the material contained in the preliminary mixer and the interior of the pump cylinder. Such known preliminary mixers have the disadvantage that the mass must not flow out of the mixing container under the action of gravity,

since the mass is ejected by the piston pump. A dosed ejection from the preliminary mixer is howevernotpos= sible since on the one hand the piston stroke is constant" and on the other hand the piston is provided with aper tures. The known preliminary mixer is thus usable only as a component of an installation requiring furtherelements.

The problem underlying the invention is toconstruct" a mixing and casting device of the: kind referred to in the introduction, which selectively enables a castable mass to be delivered in desired portions, or by which the container can be emptied without dosing of the mass.

The invention consists in a device for mixing a plurality of components of a castable mass and for casting. this mass, comprising a mixing container having a tapping region disposed at the bottom of the container and a connection for a vacuum pump, a mixing member .movable to intermediatepositions, is also able to assume at least two positions. In the first of said two positions, assumed during the mixing, the closure member permanently engages in the said bore and in the second position, assumed Q during the delivery. of the mixed mass, the closure member leaves thesaid bore, with the mixing member being in the upper region of its stroke.

Adevice constructed in this manner can be operated to effect accurate dosing of the mass, if subsequent to the bore in which the closure member is movable, a non-return valve is arranged. Without. such a nonretu'rn valve, the container can be emptied without dosing, and advantageously in this case an outlet nozzle may be arranged.

The dosing of the mass in desired portions is thus possible, since the closure member can be adjusted as desired relative to the mixing member. In the dosing position, the closure member leaves its bore, so that in the upper region of the stroke of the mixing member, the mass can flow into this bore. On entry of the closure member into its bore, the mass then contained in the bore is ejected, the ejected amount corresponding to the stroke volume in question. The stroke volume is the greater, the earlier the closure member enters into its bore. The device according to the invention also allows fine dosing by displacing the closure member with the mixing member disposed in its lowermost position. When this displacement is effected, for example by means of a threaded spindle, sensitive dosing with the smallest amounts is possible.

In the device according to the invention, the up and down drive which in any case is necessary for the mixing member is simultaneously utilised for the dosed ejection of the mass. It can thus be said that the dosing pump is combined with the mixing member, so thatthe structural costs of the device can be kept low. The device is thus well suited as a laboratory device since its structural size can be kept small and it allows the experiemental working with small amounts of casting resin.

In a particularly advantageous embodiment of the invention, the mixing member is constructed as a piston provided with openings and adapted to alternatingly enter into and withdraw from a bore arranged at the bottom of the container. In this construction, the mixing member at the same time forms a kind of charging pump which pumps the mass into the bore for the closure member. Thus, a complete filling of the bore is achieved.

In order to make the invention clearly understood, reference will now be made to the accompanying drawings which are given by way of example and in which:

FIG. 1 is a vertical section through a device according to the invention,

FIG. 2 is a cross-section along the line II-II in FIG.

FIG. 3 is a cross-section corresponding to FIG. 1 with the mixing piston lifted, and

FIG. 4 is a cross-section through an outlet nozzle.

The device has a mass container 1, a mixing member 2, a driving device 3 for the mixing member, a closure member 4, a bore 5 for the closure member 4, a displacing device 6 for the displacing of the closure member 4, and further individual parts.

The mass container 1 is cylindrically constructed in its upper part 7. A conical part 8 is connected to this cylindrical part. At the lower margin of the conical part 8, a part 9 containing the bore 5 is fixed, usually by welding. The part 9 has a cylindrical region 10 and a conical region 11 extending downwardly therefrom to the cylindrical bore 5. Generally, this bore 5 is disposed in an exchangeable cylindrical bush 12 which is somewhat bevelled at its upper rim, at 13.

In the illustrated case, a non-return valve 14 is screwed onto the part 9. This non-return valve has a movable closure part 15 which is movable in a cavity 16 of a valve housing 17 provided with a screwed-in nozzle piece 22. It is pressed against the valve seat 19 by the force of a spring 18. The movable valve part 15 has an extension 20 which in the closed position of the valve, engages in a bore 21. The bore 21 opens into the bore 5.

The entire mass container including the part 9 and the valve 17 is surrounded by a jacket 23 which at the top has an inlet opening 24 and at the bottom an outlet opening 25 for a heating medium, for example oil, which flows through the'cavi'ty 26 during operation of the device.

The mass container 1 has an upper flange 27 for supporting a cover 28. On the cover 28, a charging pipe 29 is provided which can be closed airtightly with a cover 30. Also on the cover is a connection pipe 31 for the connection of a diagrammatically illustrated vacuum pump 32. The cover 28 furthermore has a central opening 33.

The mixing member 2 is constructed as a piston the outer diameter of which is so dimensioned that it can engage with play in the cylindrical bore 10. The piston bottom 33 is conically constructed in such a manner that it can lie against the concavely conical bottom 11. The piston 2 contains a plurality of openings 34, in the present case three such openings. These openings are continued upwardly by pipes 35 which at the top are arcuately shaped in such a manner that their orifices 36 are directed towards the surface 37 of the mass. From FIG. 2 it can be seen that the pipes 35 are so arranged that the entry openings 34 and the outlet openings 36 are angularly displaced relative to each other.

An actuating rod 38 of hollow construction is connected with the piston-like mixing member 2. This rod extends through the central opening 33 in the cover 28. A piston 39 is connected with the actuating rod 38 and is movable in a cylinder 40 fixed on the cover 28. A pressure medium line 41 leads to the lower end of the cylinder 40 and a pressure medium line 42 to the upper end. The two lines extend from a changeover valve 43 which is supplied with pressure medium through a line 44. By changing over by means of the sensing member 43, the pressure medium is alternatingly fed into the lines 41 and 42 and thus the piston 39 is alternatingly acted on and accordingly moves up and down. The cylinder 40 is upwardly enclosed by a cover 45. Sealing means which are not illustrated are arranged on the piston and also on the guides of the actuating rod 38.

The piston-like mixing member contains a central bore 46 in which the piston-like closure member 4 engages. At the lower end of the bore 46 a seal 47 is provided which is engaged an annular groove in the piston 2. The diameter of the bore 46 is somewhat smaller than the diameter of the bore 5.

The closure member 4 has in its lower region an annular groove 48 in which an elastic seal 49 is arranged. At the upper end of the closure piston 4, a setting rod 50 engages which has an essentially smaller diameter than the cavity 51 in the actuating rod 38 of hollow construction, so that a certain volume remains free between the outer side of the setting rod 50 and the inner side of the actuating rod 38. At its upper end, the setting rod 50 is provided with a thread 52. A setting nut 53 which is fixedly connected with a hand wheel 54 is screwed onto this spindle 52. The nut 53 has a collar 55 at its bottom. The collar 55 is enclosed between the upper end of the actuating rod 38 and a retaining part 56 in such a manner that the nut is fixed in the axial direction but is nevertheless rotatable.

A flange 57 is fixed on the retaining part 56, and together with the retaining part defines an annular channel 58 which is in connection with the cavity 51 in the actuating rod 38 through transverse bores 59 in the actuating rod 38 and in the retaining part 56.

Instead of the valve 14, the outlet nozzle which is illustrated in FIG. 4 and designated in its entirety by numeral 60 can be used. This outlet nozzle 60 has a connection flange 61 and an outlet pipe 62. The flange 61 has the same connection dimension as a corresponding flange 61' on the valve 14.

The device operates as follows:

The liquid and pulverous components to be mixed to form a mass 63 are charged in through the charging pipe 29 with the cover 30 removed. The quantities of the components depend on the desired formula and as a rule are previously determined by weighing. The components may alternatively be introduced roughly pre-mixed. The closure member 4 is brought into such a position with the aid of the displacing rod 50, that the seal 49 on the closure member 4 engages so deeply in the cylindrical bush 12 that the seal 49 is still disposed in the bore 5 even when the mixing member 2 assumes its highest position (illustrated in FIG. 3).

After closing the charging pipe 29, the interior of the container 64 is evacuated through the line 65 leading to the vacuum pump 32. The mixer can then be actuated. Thus, the piston 39 is alternatingly supplied with the pressure medium, as a rule with compressed air, so

that the actuating rod 38 is correspondingly moved and thus also the mixing piston 2. During this up and down movement, the blocking member 4 slides up and down in the clyindrical bush 12, without withdrawing from the cylindrical bush. Accordingly, during the mixing procedure no mass can enter into the space 22 above the excess pressure valve 14.

In the uppermost position of the mixing piston 2, it is withdrawn from the cylindrical region of the part 9 (see FIG. 3). Thus, a passage 66 is freed which enables the entry of the mass 63 into the space 67 below the mixing piston 2. On the downward movement of the mixing piston 2, this gap'is closed and the mass which had passed in is placed under pressure. A part of the mass is thus squeezed through the gap between the outer surface of the piston and the piston bore surface 10, upwardly. A larger portion however is pressed through the bores 34 in the pipes 35 serving as mixing vanes and thus passes into the vacuum space 64 above the level 37 of the mass. Gas contained in the mass thus passes out of the mass andis drawn off by the vacuum pump 32 through the line 65. The necessarily occurring stationery times which result during the operation by the reversal of the direction of movement may also be artificially elongated in order that bubbles occurring during the de-gassing procedure have time to burst.

The de-gassing surface in the mixer can be increased by plates or the like which are not illustrated in the drawing, which are provided on the mixing piston 2 and dip into the mass on movement of the piston and are wetted by the mass and carry the mass on the surface when the mixing piston 2 moves upwardly, By such further vanes a considerable enlargement of the surface and also a better mixing action is obtained.

The portions of the mass which are not dislodged in the lowermost position of the mixing. piston are extremely small, since the piston 2 completely fills the lower part 67 of the container cavity and thus displaces substantially the entire mass. Thus, even the smallest constituent quantities for a charge can be just as well worked as the maximum possible charge.

The possibility of heating the mass container 1 with the aid of the heating medium flowing through the heating jacket also allows the melting of mass constituents which are liquid only athightemperatures. Instead of the indirect heating by means of a heat carrier, direct heating can alternatively be used, for example by electric heating jackets.

After mixing, the prepared mass can be fed out through the excess pressure valve 14. For this purpose, firstly by rotating a hand wheel 54, the setting rod is drawn upwardly so that the closure member 4 is drawn into the bore 56. The mixing member is drawn in so far that at the uppermost position of the mixing position 2 it no longer engages in the bore 5. Such a position is illustrated in dash dotted lines in FIG. 3. The mass can now pass into the bpre 5 through the passage 66. The mixing piston 2 now moves downwards and the seal 49 engages in the cylindrical bush 12. Sliding in is facilitated by the bevel 13. The closure member now places the mass contained in the bore 5 under pressure so thatthe excess pressure valve 14 is opened. In the lowermost position of the mixing piston, the closure member 4 has reached its deepest position and the ejection of the mass is ended. The ejected quantity is the greater, when the path is that the closure member travels through after entering into the cylindrical bush 12 is longer. It is thus readily clear that by suitable adcharge, the next charge is immediately inserted or else flushing medium is introduced forcleaning, and afedrout in the same way as the preceding charge. The flushing medium contained in the space 51 can be let into :the mass container. For this, the closure member simply has tobe displaceddownwardly so far that it comesout of engagement with the seal 47. In order to facilitate reintroduction, the closure member 4 has an upper bevel 69. v U

' For the delivery of very small mass quantities, the dosingcan alternatively be effected by rotating the hand wheel 54. In this case, the mixingpiston .2,isrin;its lowermost position, that is to say in the .positioncorresponding to FIG. 1. The space belowthe closuremember 4 is filled with the mass. If now theclosure member 4 is moved downwardly somewhat, then the mass is ejected by openingof the excesspressure valve .14. Instead of a manual adjustment with the aid of the hand wheel 54, alternatively a mechanical device may be provided which displaces theclosure member inastepwise manner. Of course, instead of a threaded spindle alternatively other displacing devices may be used,.for example a setting rod whichis constructedas a racket its upper end, in which astepwise rotatable pinionengages. Also, hydraulic displacing devices for the. setting rod are possible.

As already mentioned, instead of an excesspressure valve 14, alternatively an outlet nozzle 60 according to FIG. 4 may be used. This comes intoconsiderationiif an accurate dosing is not required. Inthis case, the mass flows out through theoutlet pipey 62, the flowing out being facilitated by the actuation ofthe mixing member. Also, a free outflow is conceivable. if themixing piston is disposed in. a raised position. However, with this kind of emptying, the vacuum in the 510308 164 has to be interrupted. When working with free outflow through a nozzle 60, the closure member does nothave to satisfy any dosing requirements but acts simply asa closure member which prevents entry of air afterthe interruption of the outflow.

It should be mentioned that the excess pressure valve 14 is so constructed that withdrawal of drops through the orifice takes place. This is achieved because due to the entry of the extension 20 of the movablervalve part 15 into the bore 21, the space 16 is enlargedyso that a suction effect occurs which withdraws the: mass drops in the orifice 70.

What we claim is:

1. Apparatus for mixing and dispensing a plurality of components formed into a castable mass comprising, in combination, a mixing container having a dispensing section disposed at the bottom thereof, vacuum. means operatively associated with said container for drawing o ff gases accumulating therein during mixing, a mixing member mounted within said container and actuated for vertical movement relative thereto to effect mixing of said castable mass. and a closure member including piston means mounted upon said mixing memberand selectively movable relative thereto, said closure member being releasably sealingly engageable with said dispensing section of said container to prevent outflow of said castable mass therefrom, said closure member also being disengageable from said dispensing section to enable dispensing of said castable mass from said container.

2. Apparatus according to claim 1 including actuating means for moving said closure member relative to said mixing member to at least two operative relative positions, with the first of said relative positions being assumed during mixing with the closure member being in continuous sealing engagement with said dispensing region of said container, and with the second of said relative positions being effected to enable dispensing of the mixed castable mass with the closure member disengaged from said dispensing section of said container, said actuating means being operable to effect said second relative position when said mxing member is in the uppermost part of its vertical stroke relative to said container and to enable said closure member to assume positions intermediate said two relative positions.

3. Apparatus according to claim 2 including valve means located within said dispensing section of said container below said closure member for enabling dispensing of said castable material in predetermined doses.

4. Appartus according to claim 3 including a valve seat defined by said dispensing section to be engaged and disengaged by said valve means to effect dispensing of said doses of said castable mass, orifice means through which said doses are delivered defined by said dispensing section on the side of said valve means opposite said valve seat, and a piston formed on said valve means and engageable with said valve seat to effect increase in the volume present between said valve means and said orifice means by enabling movement of said valve means away from said orifice means after said valve means has first become sealingly engaged with said valve seat.

, 5. Apparatus according to claim 2 including nozzle means located in saiddispensing section of said container through which said mixed mass of castable material is dispensed.

6. Apparatus according to claim 2 wherein said actuating means include a setting rod connected to said closure member and an actuating rod connected to said mixing member, said actuating rod being formed as a hollow cylinder having said setting rod arranged therein and displaceable relative thereto.

'7. Apparatus according to claim 6 wherein said set- I ting rod includes screw means operative to enable displacement of said closure member by movement of said setting rod through operation of said screw means.

8. Apparatus according to claim 7 wherein said screw means include a nut arranged at the upper end of said actuating rod, said apparatus including means mounting said nut for rotative engagement with said actuating rod but preventing axial displacement thereof, and a hand wheel mounted with said nut to enable rotation thereof thereby to effect displacement of said closure member.

9. Apparatus according to claim 6 including a fluid actuatable piston and cylinder unit operatively connected with said actuating rod for effecting vertical movement of said mixing member relative to said container.

10. Apparatus according to claim 1 wherein said dispensing section comprises a bushing defining a bore within which said closure member is sealingly engageable, said bushing being replaceably mounted within said dispensing section of said container.

11. Apparatus according to claim 1 including means defining a space through which a flushing medium may be provided, said space extending above said closure member and having its lower extremities defined by said closure.

12. Apparatus according to claim 1 wherein said closure member includes resilient sealing means located to enable said closure member to sealingly engage said mixing member and said dispensing section of said container.

13. Apparatus according to claim 1 wherein said mixing member is constructed in the form of a piston having openings therethrough, with said container defining a bore arranged to have said mixing member movable into and out of said bore during the vertical stroke of said mixing member.

14. Apparatus according to claim 13 wherein said mixing member piston comprises arcuately curved pipes in flow engagement with said openings in said piston, said pipes being directed to enable material flow from said openings to a point above the surface of the castable mass present within said container.

15. Apparatus according to claim 14 wherein said arcuate pipes comprise outlet orifices which are angularly displaced relative to said openings in said mixing member piston.

16. Apparatus according to claim 1 including a heating jacket surrounding said container.

17. Apparatus according to claim 16 wherein said heating jacket extends to surround said valve means.

' 18. Apparatus according to claim 1 including wall members arranged upon said mixing member and extending perpendicularly thereto, said wall members operating to alternately dip into and withdraw from said castable mass within said container upon said vertical movement of said mixing member to enhance the mixing effect thereof. 

1. Apparatus for mixing and dispensing a plurality of components formed into a castable mass comprising, in combination, a mixing container having a dispensing section disposed at the bottom thereof, vacuum means operatively associated with said container for drawing off gases accumulating therein during mixing, a mixing member mounted within said container and actuated for vertical movement relative thereto to effect mixing of said castable mass, and a closure member including piston means mounted upon said mixing member and selectively movable relative thereto, said closure member being releasably sealingly engageable with said dispensing section of said container to prevent outflow of said castable mass therefrom, said closure member also being disengageable from said dispensing section to enable dispensing of said castable mass from said container.
 2. Apparatus according to claim 1 including actuating means for moving said closure member relative to said mixing member to at least two operative relative positions, with the first of said relative positions being assumed during mixing with the closure member being in continuous sealing engagement with said dispensing region of said container, and with the second of said relative positions being effected to enable dispensing of the mixed castable mass with the closure member disengaged from said dispensing section of said container, said actuating means being operable to effect said second relative position when said mxing member is in the uppermost part of its vertical stroke relative to said container and to enable said closure member to assume positions intermediate said two relative positions.
 3. Apparatus according to claim 2 including valve means located within said dispensing section of said container below said closure member for enabling dispensing of said castable material in predetermined doses.
 4. Appartus according to claim 3 including a valve seat defined by said dispensing section to be engaged and disengaged by said valve means to effect dispensing of said doses of said castable mass, orifice means through which said doses are delivered defined by said dispensing section on the side of said valve means opposite said valve seat, and a piston formed on said valve means and engageable with said valve seat to effect increase in the volume present between said valve means and said orifice means by enabling movement of said valve means away from said orifice means after said valve means has first become sealingly engaged with said valve seat.
 5. Apparatus according to claim 2 including nozzle means located in said dispensing section of said container through which said mIxed mass of castable material is dispensed.
 6. Apparatus according to claim 2 wherein said actuating means include a setting rod connected to said closure member and an actuating rod connected to said mixing member, said actuating rod being formed as a hollow cylinder having said setting rod arranged therein and displaceable relative thereto.
 7. Apparatus according to claim 6 wherein said setting rod includes screw means operative to enable displacement of said closure member by movement of said setting rod through operation of said screw means.
 8. Apparatus according to claim 7 wherein said screw means include a nut arranged at the upper end of said actuating rod, said apparatus including means mounting said nut for rotative engagement with said actuating rod but preventing axial displacement thereof, and a hand wheel mounted with said nut to enable rotation thereof thereby to effect displacement of said closure member.
 9. Apparatus according to claim 6 including a fluid actuatable piston and cylinder unit operatively connected with said actuating rod for effecting vertical movement of said mixing member relative to said container.
 10. Apparatus according to claim 1 wherein said dispensing section comprises a bushing defining a bore within which said closure member is sealingly engageable, said bushing being replaceably mounted within said dispensing section of said container.
 11. Apparatus according to claim 1 including means defining a space through which a flushing medium may be provided, said space extending above said closure member and having its lower extremities defined by said closure.
 12. Apparatus according to claim 1 wherein said closure member includes resilient sealing means located to enable said closure member to sealingly engage said mixing member and said dispensing section of said container.
 13. Apparatus according to claim 1 wherein said mixing member is constructed in the form of a piston having openings therethrough, with said container defining a bore arranged to have said mixing member movable into and out of said bore during the vertical stroke of said mixing member.
 14. Apparatus according to claim 13 wherein said mixing member piston comprises arcuately curved pipes in flow engagement with said openings in said piston, said pipes being directed to enable material flow from said openings to a point above the surface of the castable mass present within said container.
 15. Apparatus according to claim 14 wherein said arcuate pipes comprise outlet orifices which are angularly displaced relative to said openings in said mixing member piston.
 16. Apparatus according to claim 1 including a heating jacket surrounding said container.
 17. Apparatus according to claim 16 wherein said heating jacket extends to surround said valve means.
 18. Apparatus according to claim 1 including wall members arranged upon said mixing member and extending perpendicularly thereto, said wall members operating to alternately dip into and withdraw from said castable mass within said container upon said vertical movement of said mixing member to enhance the mixing effect thereof. 